<!DOCTYPE html>
<html>

	<head>
		<script src="http://libs.baidu.com/jquery/1.10.2/jquery.min.js"></script>
		<script type="text/javascript">
			var countdown = 10;

			function settime(obj) {
				if(countdown == 0) {
					obj.removeAttribute("disabled");
					obj.value = "免费获取验证码";
					countdown = 10;
					return;
				} else {
					obj.setAttribute("disabled", true);
					obj.value = "重新发送(" + countdown + ")";
					countdown--;
				}
				setTimeout(function() {
					settime(obj)
				}, 1000)
			}
		</script>
	</head>

	<body>
		<input type="button" id="btn" value="免费获取验证码" onclick="settime(this)" />

	</body>

</html>